I'm thinking about using PlaceAtMe to create simple potions that appear out of thin air. If the player picks up most of them and the ones that are not picked up are deleted with DeleteReference, will this still bloat the savegame?

EDIT: I can use AddItem on an actor and then Drop to achieve the same effect, but it'd still be good to know

First of all "PlaceAtMe" and "AddItem+Drop" have EXACTLY the same effect on the savegame size.
Both create a new item out of nothing and the item's information will take some space in the savegame.

If (1) the player picks up the item, (2) you use DeleteReference on the item or (3) an NPC is correctly scripted to pick up the item ("Item.Activate NPC 1"), then the item's info is removed from the savegame.

Also, cell reset cleanup routines are supposed to remove those items (but I don't really know how much we can count on it - or http://www.tesnexus.com/downloads/file.php?id=24606 mod would not be so popular)